Wildcat · Wildcat
.300 Whisper
The .300 Whisper is a wildcat cartridge developed by J.D.
- Caliber
- 0.3084″ · 7.833 mm
- Introduced
- 1992
- Case
- Rimless
- Parent
- .221 Remington Fireball
- Primary use
- suppressor_use, hunting_small_game, military_special_operations
- Status
- Obsolete
- Introduced
- 1992
- Type
- Wildcat
- Origin
- United States
- Inventor
- J.D. Jones
- Manufacturer
- SSK Industries
- Standard
- Wildcat
- Status
- Obsolete
- Availability
- Handload Only
- Case capacity
- 26.5 gr H₂O
- Twist (typical)
- 1:8
- Primer
- Small Rifle
- Case type
- Rimless
- Max pressure
- 25,000 psi
- Eff. range
- 250 yd
- Recoil
- 4–7 ft·lb
- Subsonic
- Capable
Ballistics
Published velocity/energy data isn't available for .300 Whisper — an obsolete/collector cartridge. Parent case: .221 Remington Fireball.
Performance
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
CIP TDCC · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 7.83 | 0.308 | ✓ |
| Neck ⌀ | 8.46 | 0.333 | ✓ |
| Shoulder ⌀ | 9.14 | 0.360 | ✓ |
| Shoulder angle | 23° | — | ✓ |
| Base ⌀ | 9.54 | 0.376 | ✓ |
| Rim ⌀ | 9.60 | 0.378 | ✓ |
| Belt ⌀ | n/a | ||
| Rim thickness | 1.14 | 0.045 | ✓ |
| Neck length | 6.75 | 0.266 | ≈ |
| Case length | 34.82 | 1.371 | ~ |
| Overall length | 57.20 | 2.252 | ~ |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .300 Whisper is highlighted below.
Factory loads
Being verified
Advertised FPS, energy, and BC are withheld until loads clear verification.
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Firearms chambered in .300 Whisper
1 model in the database chamber .300 Whisper. Browse all →
Lineage
Connected reference
History
J.D. Jones designed the Whisper concept around the .221 Remington Fireball case, which fits in a standard AR-15 bolt face while providing enough case capacity for heavy .30-caliber subsonic loads. The cartridge gained a following in military special operations communities and among suppressor enthusiasts. Advanced Armament Corporation (AAC) later developed the .300 AAC Blackout as a SAAMI-standardized version with input from the military, achieving essentially the same ballistics with standardized dimensions.
FAQs
- What twist rate does .300 Whisper use?
- .300 Whisper typically uses a 1:8 twist rate.
- What bullet diameter is .300 Whisper?
- .300 Whisper uses a 0.3084″ (7.833 mm) diameter bullet.
- Is .300 Whisper still in production?
- .300 Whisper is obsolete; typical availability is handload only.
- What is .300 Whisper used for?
- .300 Whisper is primarily used for suppressor_use, hunting_small_game, military_special_operations.
- What is .300 Whisper based on?
- .300 Whisper is derived from the .221 Remington Fireball case.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 14 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →